Carica papaya commonly known as papaya, is a native of tropical America. It belongs to the genus Carica, a member of family caricaceae. The plant adapts itself to diverse soil and climatic conditions, and hence is grown extensively in tropical and subtropical areas for its profitable and continuous yield of fruits. The fruits arc mostly consumed ripe and are a rich source of vitamins A, B, C, and D. (Kumar et al, J. Born Natural His. Society, vol. XV no. 2, Dec 43, 252-256). A milky latex is extracted out of 25 young green fruits. This latex contains a high percentage of papain, which is one of the most valuable of plant proteolytic enzymes. Papain is of interest to many industries especially the food industry which is one of its biggest consumers. Papain is used for chillproofing beer, tenderizing meat and freeing food proteins. It is used in peptone preparation from meat and milk in bacteriological laboratories, in textile industry for degumming of silk in dairy industry for cheese preparation, in tanning industry for skin dehairing and bating of hides, in pharmaceutical industry, perfume industry and in effluent treatment. Papain is also used to produce animal feed products and recover animal wastes by digestion of proteins. (Jones et al, Process Biochemistry 9, (1976) pp. 21-22) Papaya plants are propagated through seeds. The seeds are sown in seed beds and 1-2 months old seedlings are transplanted to the field. 2-3 seedling are planted in one pit, as the sex of the seedlings is unknown. Plants attain reproductive maturity after 5-8 months. Most of the male plants are then uprooted from the field. This unnecessary cultivation and uprooting leads to wastage of time, money and labor.
The dioecious cultivars are preferred for the extraction of papain as the female yield of crude papain exceed that of hermaphrodite and also the proteolytic activity of the crude papain from female fruits is greater than hermaphrodites. (Madrigal et al., J. Sci. Food Agri 1980,31: 279-285).
Breeding programs are initiated with objectives to evolve disease resistant and true breeding papaya varieties with good quality fruits and high papain content. The dioecious nature poses problems and inconvenience to papaya breeders and growers since it takes 5-8 months to know the sex of the seedling. Unfortunately, the sex cannot be deduced from external morphology or cytology with embryonic or juvenile forms. If the sex of plants is known at the juvenile state, it would facilitate screening of the seedlings for female plants thereby saving time and economic resources and thereby helping in the breeding program.